The α-(1,3)-glucan synthase gene agsE impacts the secretome of Aspergillus niger

Aspergillus niger is widely used as a cell factory for the industrial production of enzymes. Previously, it was shown that deletion of α-1–3 glucan synthase genes results in smaller micro-colonies in liquid cultures of Aspergillus nidulans . Also, it has been shown that small wild-type Aspergillus niger micro-colonies secrete more protein than large mirco-colonies. We here assessed whether deletion of the agsC or agsE α-1–3 glucan synthase genes results in smaller A. niger micro-colonies and whether this is accompanied by a change in protein secretion. Biomass formation was not affected in the deletion strains but pH of the culture medium had changed from 5.2 in the case of the wild-type to 4.6 and 6.4 for Δ agsC and Δ agsE, respectively. The diameter of the Δ agsC micro-colonies was not affected in liquid cultures. In contrast, diameter of the Δ agsE micro-colonies was reduced from 3304 ± 338 µm to 1229 ± 113 µm. Moreover, the Δ agsE secretome was affected with 54 and 36 unique proteins with a predicted signal peptide in the culture medium of MA234.1 and the Δ agsE, respectively. Results show that these strains have complementary cellulase activity and thus may have complementary activity on plant biomass degradation. Together, α-1–3 glucan synthesis (in)directly impacts protein secretion in A. niger .